Since the iPhone was introduced, people have been jailbreaking the device so they can tether their computers and other devices to it to access the internet. But in the last few says, a number of readers have written us after receiving an e-mail from AT&T indicating that the Death Star is onto their jailbreaking ways and would kindly like you to stop.

Reads the e-mail from AT&T:

We’ve noticed your service plan may need updating.

Many AT&T customers use their smartphones as a broadband connection for other devices, like laptops, netbooks or other smartphones — a practice commonly known as tethering. Tethering can be an efficient way for our customers to enjoy the benefits of AT&T’s mobile broadband network and use more than one device to stay in touch with important people and information. To take advantage of this feature, we require that in addition to a data plan, you also have a tethering plan.

Our records show that you use this capability, but are not subscribed to our tethering plan.

If you would like to continue tethering, please log into your account online at http://www.wireless.att.com, or call us at 1-866-679-7118 Monday – Friday, 7 a.m. – 9 p.m. CST or Saturday, 8 a.m. – 7 p.m. CST, by May 13, 2011 to sign up for DataPro 4GB for Smartphone Tethering….

If we don’t hear from you, we’ll plan to automatically enroll you into DataPro 4GB after May 13, 2011. The new plan – whether you sign up on your own or we automatically enroll you – will replace your current smartphone data plan, including if you are on an unlimited data plan.

If you discontinue tethering, no changes to your current plan will be required.

One Consumerist reader who received this kindly worded warning, and who still has his original “unlimited” data plan, brought up the point that so many others have raised before: If he has an unlimited data plan already, why should he have to spend another $20 per month for AT&T’s 4GB DataPro tethering plan?

Regardless, for those of you that have tinkered with your iPhone, be aware that AT&T is onto you and is frowning with disapproval.